1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly, to an indicator for deciding a grinding amount of liquid crystal display panel and a method for detecting grinding failure using the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for simplifying a grinding detection process in grinding a marginal portion of a unit liquid crystal display panel after cutting into the unit panels from the large mother substrate.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) panel is cut into a plurality of unit LCD panels to improve yield. For simultaneously producing LCD panels, a plurality of thin film transistors and color filters are formed on two different mother substrates. Thereafter, the two mother substrates are attached to each other.
Conventionally, cutting of the unit LCD panel is performed through the process of forming a scribing line on the surface of the mother substrate with a wheel having a hardness higher than glass and breaking the mother substrate scribing line. The process for fabricating an LCD apparatus will be described with reference to the accompanied drawings.
FIG. 1 is a schematic cross-sectional view illustrating a first mother substrate including thin film transistor array substrates and a second mother substrate including color filter substrates. The first and second mother substrates are attached to each other, thereby forming a plurality of unit LCD panels.
With reference to FIG. 1, the unit LCD panels are formed so that one side of thin film transistor array substrates 1 is formed to be protruded more than color filter substrates 2. This is because a gate pad unit (not shown) and a data pad unit (not shown) are formed at the marginal portion of the thin film transistor array substrates 1 that-do not overlap the color filter substrates 2.
Therefore, the color filter substrates 2 formed on the second mother substrate 30 are formed apart for the area of a dummy region 31 corresponding to the region where the thin film transistor array substrates 1 are protruded on the first mother substrate 20.
Also, the respective unit LCD panels are positioned to effectively utilize the first and second mother substrates 20 and 30. The unit LCD panels are formed apart for the area of the dummy region 32 depending on the model.
The first mother substrate 20 where the thin film transistor array substrates 1 are included, and the second mother substrate 30 where the color filter substrates 2 are included, are attached to each other. Thereafter, the LCD panels are cut into an individual panel. The dummy region 31, where the color filter substrates 2 of the second mother substrate 30 are formed, and the dummy region 32 for separating the unit LCD panels are simultaneously removed at this time.
After cutting the second mother substrate 30 into the unit LCD panels, a shorting line formed at the marginal portion of the thin film transistor array substrate 1 for intercepting static electricity is removed. In this process, a sharp corner of the unit LCD panel is ground. The static electricity may occur at the shorting line when a conductive film is formed on the thin film transistor array substrate 1. Also, by grinding the sharp corner of the LCD panel, pieces are not separated from the corner of the unit LCD panel by the external impact and prevent an operator from being damaged by the sharp corner of the unit LCD panel in the fabrication process.
The method for grinding the conventional unit LCD panel and a method for detecting a grinding amount will be described in detail with reference to the accompanied drawing.
FIG. 2 is a schematic plane view of the conventional unit LCD panel.
With reference to FIG. 2, a unit LCD panel 10 includes a picture display unit 13 that liquid crystal cells are arranged in a matrix form, a gate pad unit 14 for connecting a plurality of gate lines GL1 to GLm of the picture display unit 13 to a gate driver integrated circuit (not shown), to which a gate signal is applied, and a data pad unit 15 for connecting a plurality of data lines DL1 to DLn of the picture display unit 13 to a data driver integrated circuit (not shown), to which the picture information is applied. The gate pad unit 14 and the data pad unit 15 are formed at the marginal portion of the thin film transistor array substrate 1 where both side edges are protruded comparing to the color filter substrate 2.
At the region where the data lines DL1 to DLn and the gate lines GL1 to GLm vertically cross one another, a thin film transistor for switching the liquid crystal cell is formed therein. A pixel electrode is formed to be connected to the thin film transistor for driving the liquid crystal cell. A passivation film is formed on the entire surface to protect the data lines DL1 to DLn, the gate lines GL1 to GLm, the thin film transistors, and the electrodes.
Also, a shorting line (not shown) for electrically shorting out the conductive films is formed at the marginal portion of the thin film transistor array substrate 1, to remove static electricity which may be generated in forming the data lines DL1 to DLn, the gate lines GL1 to GLm, and the electrodes on the thin film transistor array substrate 1.
At the color filter substrate 2 of the picture display unit 13, a plurality of color filters are coated and separated by cell regions with a black matrix. A common transparent electrode corresponding to the pixel electrode is formed at the thin film transistor array substrate 1.
A cell gap is formed between the thin film transistor array substrate 1 and the color filter substrate 2 so that the two substrates are spaced apart and face into each other. The thin film transistor array substrate 1 and the color filter substrate 2 are attached by a sealing unit (not shown) formed at the exterior of the picture display unit 13. A liquid crystal layer (not shown) is formed at the space between the thin film transistor array substrate 1 and the color filter substrate 2.
On the other hand, a plurality of tap marks 50a to 50j are formed and separated from one another for aligning the data lines DL1 to DLn, the gate lines GL1 to GLm to contact a plurality of pins of the gate driver integrated circuit and the data driver integrated circuit.
The above unit LCD panel 10 must be ground to have a sloped edge from the end of the unit LCD panel 10 to the grinding line R1, as shown in the expansion region EX1 of FIG. 2. However, the actual ground line of the unit LCD panel 10 has an error margin D1 from the grinding line R1. When the error is beyond the error margin D1, it is determined that the grinding is defective.
To detect the failure, an operator must separate the ground unit LCD panel 10 from the production line for a predetermined period. Thereafter, an additional apparatus should be used to determine whether the actual ground line of the unit LCD panel 10 is beyond the error margin D1 by using a high magnifying power camera or a projector positioned in the measuring apparatus.
In the method for the grinding detection of the conventional liquid crystal display panel, the ground unit liquid crystal panel 10 is separated from the production line for a predetermined period. Then, the unit LCD panel is measured by using an additional apparatus to determine whether the actual ground line of the unit LCD panel 10 is beyond the error margin D1 with a high magnifying power camera or a projector positioned in the measuring apparatus.
As described previously, the operation of examining the grinding amount with the measuring apparatus, after the operator separates the unit liquid crystal panel from the production line to measure the grinding amount of the cut unit LCD panel, is complicated and inconvenient. Thus, productivity is decreased as much as the time for measuring the grinding amount of the unit LCD panel.
As a costly measuring apparatus is additionally required, installing cost as well as maintaining and repairing costs are increased, thereby increasing cost of products.
Also, since the measurement of the grinding amount is performed by sampling the unit LCD panel for a predetermined period, reliability of the examination is lowered. Also, the completed unit LCD panels may be disposed. The operation is stopped and the grinding amount of all liquid crystal display panels including unsampled panels should be measured when the grinding is defective. Accordingly, there is significant waste in raw materials and time.